The conventional home sewing machine has either one or two needles and in combination with a bobbin forms a seam which, when executed properly, generally unites two or more pieces of material.
Another type of sewing machine, initially called an overlock machine, now more commonly referred to as a serger, has been made available to the home sewer. The serger cuts the fabric being fed into the machine and the loopers and needles encase the cut edge of the material with a chain-like edge of thread or other flexible filament to prevent the cut edge from fraying. In the case of only one layer of fabric introduced into the machine, the serger cuts and encapsulates. In the case of more than one layer of fabric being introduced into the machine, the serger cuts, encapsulates and unites, all in one operation. The stitch fingers, i.e., small projections or prongs on the needle plate or presser Foot then feed the stitches encasing the fabric off the machine.
Like most conventional sewing machines, the serger uses one or two needles. Unlike most conventional sewing machines, the serger has no bobbin; therefore in some respects the loopers replace the work of the bobbin. Thus a series of loopers along with the needles perform the sewing operation.
Different models of sergers utilizing from two to five spools of thread are available with each machine offering various types of stitches; however for the purpose of describing the invention herein, a machine utilizing four spools of thread with two needles and two sets of loopers will be described. The present invention functions satisfactorily with any serger sewing machine.
In addition to other mechanisms found on the machine not strictly relative to the invention, sergers have thread guide bars, tension discs and guides which create a thread path. A four-spool serger would have four bar guides, four tension discs and approximately 12 thread guides. Thread path information is posted on each machine and if followed correctly, makes threading of the guides, discs and thread guides relatively easy as the guides, discs and thread guides are positioned both on top and on front of the serger. The front of the machine faces the operator thereby placing bars, discs and guides in plain view.
Threading the loopers is another matter as they are located in an almost-impossible-to-reach cavity beneath the working surface of the machine.
All threading is done sequentially: bar guides, tension discs, thread guides, upper looper, lower looper and finally the needle or needles. Flexible filaments are withdrawn from spools placed on spindles to the rear and/or side of the machine. The filament or, in case of more than one, filaments are drawn from each spool one at a time by hand and placed through each relative bar guide, tension disc and thread guide until thread and/or threads have been drawn from all the corresponding spools and all bar guides, tension discs and thread guides have been threaded and the filaments are now ready to be passed through the eyes of the upper looper, lower looper and needle or, in case of two needles, needles.
Each looper contains two eyes and because they are in the heretofore mentioned difficult-to-reach undercarriage of the serger, threading the looper eyes is virtually impossible without the aid of some type of threading device.
In some cases tweezers are used to thread the eyes of loopers. For purposes of clarity let us assume that one length of thread is being used in each needle, therefore it is herein assumed the operator has drawn the thread through the bars, discs and guides and is prepared to thread the loopers. The operator must pinch the cut end of the thread between the opposed, pointed end of the tweezers and carefully insert the cut end through the looper eyes. The application herein described is difficult to manage because of the confined area wherein the loopers are placed therefore this threading technique is generally not within the scope of manual dexterity of many operators.
Another method of threading is to use a fine wire loop which has been encased within one end of a relatively long metal tube holder having a tab handle at the opposite end of the wire loop. After drawing the thread by hand through bars, discs and guides, the operator need pierce each looper eye with the fine wire loop, thereinafter pass the wire loop through the eye, thread the leading cut end of the flexible filament through the already inserted wire loop then withdraw the loop from the eye, leaving the flexible filament passed through that particular looper eye. This procedure must be practiced for each eye in each looper. The wire in the wire threader, by necessity, is so fine that it bends and ultimately breaks after being used only a few times. As heretofore mentioned, the space herein described is extremely limited and the length and rigidity of this wire loop threader precludes a swift threading procedure.
Specific instructions as to correct threading procedure are provided with each individual serger machine and must be followed exactly if the serger is to operate properly. If the serger is threaded incorrectly or if the sewing threads become tangled or if the sewing threads become broken, the machine will not stitch properly and the threading procedure must be repeated from the beginning and if the color of the thread needs to be changed, the threading process must be repeated from the beginning.
The needles are threaded thereafter.
U.S. Pat. No. 4,667,860 discloses a needle having a trailing deformable loop made of thin spring steel wire, flexible plastic or other deformable material while the body of the needle is formed of a rigid material such as steel hypodermic tubing. The rigid body of this device would not allow the device to negotiate the constrictive cavity of the undercarriage of a serger. Therefore the inadequacies of this invention for threading a serger sewing machine are evident.
U.S. Pat. Nos. 3,929,144 and 4,133,339 disclose a looped filament for guiding dental floss between a person's teeth. The looped filament is not formed in a manner that would permit it to be used to thread the intricacies of the serger because the thread could be easily separated from the device.